Check the back of your TV. Are the vent ports clean and free of lint? Lint build up will impede the airflow necessary for the interiors components. Clean them using a dust wand or a can of air. At some point it'll lead to a blown capacitor. That's noted either by a bulge at the top or a brownish substance. If you're handy with a soldering gun is a relatively easy fix. If not, then you would need to replace the board with the blown capacitor.